Abstract

The isovalent substitution of for substitution in the recently discovered misfit cobaltite has been investigated for its very attractive thermopower properties. Starting from the pure Sr cobaltite with a thermopower S value at 300 K in the range from 100 to 130 μV it is found that the calcium substitution enhances the thermopower value up to +165 μV for the pure calcium phase, Since these thermoelectric materials are studied for the high T applications, it should be pointed out that this S improvement induced by chemical substitution is even more pronounced for K with μV This beneficial effect is interpreted in the light of the clear modification in the geometry of layers which could play a role on the cobalt electronic configurations.